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330                 PATHOGENIC BACTERIA.

The Spirillum of Denecke.—Another organism with
a distinct resemblance to the cholera spirillum is one
described by Denecke as occurring in old cheese (Fig.
87). Its form is much the same as that of the spirillum
of cholera, the shorter individuals being of equal diameter
throughout. The spirals which are produced are longer
than those of the Finkler and Prior spirillum, and are
more tightly coiled than those of the cholera spirillum.

Like its related species, this micro-organism is actively
motile. It grows at the room-temperature, as well as at
37° C., in this respect, as in its reaction to stains, much
resembling the other two.

Upon gelatin plates the growth of the colonies is much
more rapid than that of the cholera spirillum, but slower
than that of the Finkler and Prior spirillum. The col-


FIG.  87.—Spirillum Denecke, from an agar-agar culture;   x 1000 (Itzerott
and Niemann).

onies appear as small whitish, round points, which soon
reach the surface of the gelatin and commence liquefac-
tion. By the second day they are about the size of a
pin's head, have a yellow color, and occupy the bottom
of a conical depression. The appearance is much like
that of a plate of cholera spirilla.

The microscope shows the colonies to be of irregular